Some electronics books from the 50s claimed making triode tubes would be an impossible endeavour for amateurs. Today, there are at least two DIY laboratories making not only triodes but also all sorts of vacuum electron devices.

Three years after the first GPS satellite was launched, few people used the technology, which was perceived as very complicated and expensive. Yet, someone successfully operated his homebrew receiver made from hundreds of that time’s electronic parts.

These days, microchips are often thought to be impenetrable and
impossible to manufacture without large-scale facilities. But many individuals are reverse engineering microelectronics designs, often breaking security systems based on the obscurity of the silicon layout. Some are even devising DIY methods to replicate parts of the microchip manufacturing process, with impressive results.

What are the frontiers of DIY technology? The first Exceptionally Hard & Soft Meeting (EHSM) will feature presentations of the brightest DIY achievements. But we do not want to stop at DIY. In fact, we should not, because teamwork is the only way to get the big things done.

The open source ethos is about keeping the freedom and openness of DIY when many people are involved. At a time when thousands of developers from hundreds of companies contribute to Linux and the world’s largest physics laboratories share openly licensed hardware designs on OHWR, we will explore the cutting-edge open source hardware and software practices.

This premiere of the EHSM will be held in Berlin on December 28-30 2012. Everyone is welcome to attend it. Curiosity is enough to qualify, and we have kept the minimal entrance fee affordable. Please order your ticket as soon as possible, to help us make this event happen.

They are already coming
To give you an idea of what is coming up, we are pleased to announce that the following speakers will be presenting their awesome work:

• Jeffrey Gough will talk about and demonstrate metalwork techniques. How to go beyond extruded ABS coming from a 3D printer? There might even be a hands-on workshop coming up, stay tuned.
• Shawn Tan has been working on a new open source microprocessor design and will introduce it at EHSM.
• Ben Krasnow makes all sorts of seemingly impossible science experiments at home, such as creating aerogel (yes, that thing on spacecraft), Pop Rocks candy, or building a scanning electron microscope. He will talk about a yet undisclosed but promising topic.

More speakers will be announced as we confirm them, check this space!

Tickets and funding
EHSM is entirely supported by its attendees and sponsors. To help us make this event happen, please donate and/or order your ticket as soon as possible. EHSM is a non-profit event and most of the money will be used to cover speakers’ travel expenses.

Submit your presentation
Since we do not pretend to be aware of all the amazing tech out there, we are expecting your proposals.

Send a mail to orga AT ehsm.eu with at least the following information:

• Name of the speaker
• Short bio of the speaker and/or his/her team
• Speaker contact information (e-mail + mobile phone if possible)
• Where the speaker will be traveling from
• Title of the presentation
• Abstract
• Links to more information (if available)

The standard format for presentations is one-hour lectures, but we are flexible. Write us a note if you have special time or other requirements.

We are waiting for your presentations in these areas:

• Open hardware
• Big open source project management
• Licensing and business models for open source
• Manufacturing: metalwork, glass blowing, …
• Electronics engineering
• Signal processing
• Radars
• Semiconductors
• Rocket science
• Thin film technologies
• Hardware acceleration
• Satellite design
• Vacuum electron devices
• Millimeter wave technology
• Reverse engineering
• Applied quantum physics
• Thermodynamics
• Nuclear science
• Nanotechnologies
• Ultra high speed photography

…and anything awesome which is not listed here.

If you know of someone else’s work that would be relevant, feel free to tip us! (orga AT ehsm.eu)

For academia
While researchers are most welcome to present their work at EHSM, please note that this is not a traditional academic conference. We will not formally publish proceedings(*), and we do not claim affiliation with any institution. We are also OK with previously published work, we simply expect high-quality presentations.

(*) Contrary to the practice of most academic publishers, we will, however, do our best to ensure the free dissemination of information.

Dates
Doors open: December 28th, 2012, 09:00
Doors close: December 30th, 2012, 18:00
Early registration fee ends: July 15th, 2012
Submission deadline: November 21st, 2012
Notifications of acceptance : November 28th, 2012 (or sooner)
Full programme published: November 28th, 2012

Venue
TU Berlin, Hörsaalgebäude Elektrotechnik
Lecture room HE101
Straße des 17. Juni 136
10623 Berlin, Germany
U Bahn: Ernst-Reuter-Platz

We thank TU Berlin and Freitagsrunde for providing the venue.

WE ARE LOOKING FORWARD TO WELCOMING YOU IN BERLIN!
- the EHSM organizing committee

The first step was to build a variable high voltage power supply, since I’m under-equipped enough not to have one laying around. So I used a 20V power supply transformer connected to a 120V variable autotransformer scavenged from a 70′s American-built X-ray machine that happened to have a permanent tap within the first turns, allowing it to step-up the voltage to a nice 180V. For turning it into DC, I simply took the switching power supply PCB from a discarded fax machine, cut it right after the filtering capacitor, and hooked it to the variac. There are easier options, but I did with what I found in my pile of junk

The grid voltage is provided by a 9V battery and a potentiometer, and the filament voltage by my (single!) lab power supply. I then used cheap DMMs to measure anode voltage, anode current and grid voltage.

This resulted in this little kludge:

Experimental setup

Schematics of the above little mess

Emission tests
The first test was to see how many electrons the hot filament is capable of sending into the tube. I connected together the anode and the grid and brought them to a 176V potential, while I varied the filament voltage.
This led to this plot:

Cathode emission versus filament voltage

The second test was to see how much the anode potential influenced the anode current. I set the grid to the ground potential, and varied the anode voltage. The plot shows a quite linear dependence:

Anode current versus anode voltage

Amplification test
Now, let’s see how good this triode is at doing its job: amplifying signals! With the anode potential set to 176V and a filament voltage of 4V, I sweeped the grid voltage and plotted the anode current:

Anode current versus grid voltage

First – it is awesome. The amount of ingenuity that Aleksander Zawada, who runs PWL, has had to keep his hobby affordable is remarkable. I particularly liked the microwave oven transformer based spot welding machine, and the hacked turntable used to spin glass while melting it (more on this later). Before the laboratory moved to its current premises in the Institute of Vacuum Technology, Aleksander started everything in his own private apartment.

PWL was recently moved into the Institute of Vacuum Technology in Długa street, Warsaw

Aleksander was kind enough to show me the full making of a triode. But mind you – he does not stop at triodes. The place is full of contraptions that he built: canal ray tubes, a RGB magic eye, several Crookes tubes, multiple (still untested) attempts at making Geiger tubes, and many other incredibly amazing devices.

He starts the triode by assembling the grid. To do this, he takes a piece of nickel wire, and soldered a small spiral of molybdenum wire on it – one turn and one solder at a time. He uses molybdenum because of its low emission of free electrons when heated (which causes unwanted grid current in tubes) and its high melting point. Soldering is done with a spot welding machine, which passes high current through the parts to be soldered (nickel and molybdenum wires). The current is so high that the metals heat and melt locally and form a small solder spot. How does one obtain such a high current? Aleksander simply took the transformer of a microwave oven, removed the high voltage secondary, and wound instead a few turns of a thick aluminum bar whose ends are connected to the copper electrodes of the welding machine. The solder current can be controlled by a triac-based dimmer connected in series with the transformer’s primary.

Spot welding machine at PWL

Aleksander then prepares the tube’s anode, which is simply a small piece of metallic sheet bent into a cylinder. He then solders everything together into the lamp base, which consists in a piece of glass with four electric wires going through it in a vacuum-tight fashion. This part was pre-made to save time, but he showed me a few ones that he built. The assembly included the tungsten cathode – yes, the spot welder can melt tungsten – and the barium-based flashed getter reservoir. The directly heated tungsten cathode is the simplest one can make, but Aleksander is also able to make cathodes coated with substances such as yttrium oxide for better electron emission capacity.

Before the electrodes are ready, Aleksander cleans them with a series of ultrasonic baths filled with three different solvents. The purpose of this treatments is to remove fingerprints and other organic deposits, which would otherwise evaporate and ruin the vacuum.

The completed electrode assembly

Now is time to prepare the lamp’s bulb. First and foremost – imprint a PWL logo into it. He uses a stamp with a special formulation of paint which, when heated, melts into the glass and marks it permanently.

Stamping the bulb

Melting the paint into the glass

As a cheap source of bulbs, Aleksander uses glass enclosures he easily obtained from light bulb factories – they had plenty of surplus stock when incandescent lights were removed from sales in Europe.

Now, let’s assemble the electrodes and the bulb together. He does that by melting the bulb into the base, by rotating it and heating the bottom with a propane torch. Of course, the spinner is also made of junk materials – this time, a turntable that was originally intended to play vinyls.

Assembling the base and the bulb

After the tube has been heated so much, the cool-down must be very slow or the glass would break. Aleksander has a small electric oven for this purpose, into which he places the tube to ensure a safe return to room temperature.

Triode cooling down

Ok, now the tube is cooling down, and the vacuum pumps are getting ready. In the meantime, why not have a look at those phosphor-coated screens in this corner of PWL?

Fluorescent screens

Aleksander supplies some to a nuclear research facility about 30km of Warsaw, where they are used as X-ray fluorescent screens. He makes them using two methods. The first one, the simplest, consists in roughening the screen’s surface using glass powder scratched into it, in a process similar to using sandpaper. He then applies the phosphor powder, which gets into the microscopic grooves of the scratched screen surface and adheres to the glass. Note that the phosphor often does not actually contain phosphorus, but other chemicals such as zinc sulfide and europium, depending on the color and other properties.

Salt shaker filled with phosphor

The other method is based on sedimentation. Aleksander prepares a suspension of the phosphor powder in water, filters it to keep only the smallest grains, and adds a mixture of potassium silicate and strontium nitrate which helps with bonding the phosphor to the glass. The powder slowly sinks to the bottom and attaches itself to the glass.

Beep! Beep! The vacuum system calls for our attention. The diffusion pump has reached its working temperature and is now ready to evacuate our triode. Aleksander obtained the pump from the garbage of a research institute, and attached to it a primary mechanical pump in the common two-stage configuration for high vacuum systems.

Vacuum pumps at PWL

The lamp base has a glass tube going through it which is used to drain the air from the tube. With a small hand-held propane torch, Aleksander welds it to the business end of the vacuum system, and before opening the valve that would empty the tube, uses a high voltage power supply connected to the tube’s electrodes to establish a series of sparks into the glass bulb. Those are used to verify that the tube is actually being emptied of its air. After he opens the valve, the sparks gradually turn into a pale blue glow that fills almost the entire tube, before disappearing almost completely. It’s working! But we are not there yet. Electrodes can hold a significant quantity of gases that would slowly expand into the tube, damaging the vacuum and drastically shortening the tube’s life. To get those gases out, he heats the tube’s parts glowing hot while the vacuum pump keeps running.

Cathode degassing

The most straightforward electrode to degas is the cathode. He simply runs an electrical current though it, until it becomes glowing white. On the vacuum gauge, the pressure rises as the extreme heat releases the gases trapped in the tungsten filament.

Then comes the grid. Since we have a working cathode emitter, why not bombard it with electrons to increase its temperature? With the cathode still glowing, he applies several hundred volts to the grid. Again, the pressure rises temporarily, until the vacuum pumps permanently rid the tube of those unwanted trapped gases.

The anode is a little more complicated. Using electron bombardment is more difficult, because the cathode as a limited emission capability and the is much bigger than the grid and therefore difficult to heat. But Aleksander has built a portable induction heater, which he uses to make the anode red-hot in a few seconds.

He is now ready to remove the tube from the vacuum system. This is simpler than you might think – with the propane torch, he heats the draining glass tube, which melts and nicely seals the tube.

One last step is required before the triode is ready: flashing the getter. In no time, the induction heater makes the little ring containing the getter materials glowing red-hot. Chemical reactions inside it produce pure barium, which evaporates and condensates in a silvery deposit on the tube’s walls. Barium is a very reactive element, which captures substances such as residual air in the tube and helps prolonging the triode’s life by making the vacuum better.

All is needed now is to solder a socket to the base of the triode, and use it to make (for example) a regenerative radio receiver!

The completed triode

I would like to thank Aleksander for this awesome visit. Keep up the good stuff!

For more information you can check out his homepage and my complete picture collection.